Slipping Clutch/ Contamination Issue

[mark4g63t]

Don't want to go twin disc as it's totally unnecessary for my power goals right now and I do eventually plan to go AWD.
What did they change? I know the disc went from 6 to 4 springs, but did they also do something to the PP or flywheel? Both my pressure plates have been used ones. One was the older part number and the one in it now is the newer part number. They had low miles, but were used none the less.
I'm really starting to think it's the flywheel being resurfaced too many times (i'm sure the previous owner had resurfaced it at least once) now there is not enough material? But I thought that pedal adjustment and shimming would make up for that?